1. Field of the Invention
This invention comprises the use of non-toxic sparingly soluble calcium and phosphate compounds as additives to chewing gums, candies, confectioneries, gels, toothpastes or dentifrices that cause the release of calcium and phosphate ions into the oral cavity gradually and persistently for an appropriate and therapeutically useful period. The released calcium phosphate ions can diffuse into partially demineralized tooth enamel or dentin, leading to remineralization and repair of the caries lesion. The released calcium phosphate ions can also diffuse into dental plaque to cause remineralization of teeth and to reduce or eradicate cariogenic challenge in plaque following sucrose intake. Thus, these formulations can produce effective anticaries actions without the use of fluoride. The released calcium phosphate ions can also cause precipitation of calcium phosphate minerals inside open dentinal tubules and on exposed dentine surfaces to desensitize hypersensitive teeth. These agents will have minimal adverse effects and require little effort on the part of the user.
2. Summary of the Related Art
Chewing gums have the potential of being an effective vehicle for delivering therapeutic agents to teeth because they permit protracted contact of the agent to the teeth with minimal effort on the part of a patient. Despite the recognized desirability of chewing gums as vehicles for delivering anticarious agents to teeth, no effective embodiments of anticarious chewing gums have been developed in the art.
The effectiveness of prior attempts at using potential anticarious agents in chewing gums was reviewed by Edgar and Geddes (1990, Br. Dent. J. 24: 173-176). For example, dicalcium phosphate dihydrate (DCPD; CaHPO.sub.4 .multidot.2H.sub.2 O), was used at a dose of 7.5 wt % and assessed for its effects on the calcium (Ca) and phosphate (PO.sub.4) concentrations in saliva (Pickel and Bilotti, 1965, J. Alabama Med. Soc. 2: 286-287). A chewing gum containing 10 wt % DCPD was assessed for anticarious effects in two different clinical studies (Finn and Jamison, 1967, J. Amer. Dent. Assoc. 74: 987-995; Richardson et al., 1972, J. Canad. Dent. Assoc. 6: 213-218). The results from the Richardson study showed that, although sugar-DCPD gum produced a lower caries score than did the gum containing sugar alone, the cariogenicity of the sugar-DCPD gum was equivalent to that of sugar-free gum. The marginal degree of effectiveness of DCPD as an anticaries gum additive in this study was accepted in the art as demonstrating that DCPD was ineffective as an anticarious agent. As a result of this study, there has been little interest or activity in the art in using calcium phosphate-containing gums as anticarious agents.
Recently, the feasibility of using two new calcium phosphate additives in bubble gum has been evaluated for effectiveness in increasing salivary mineral saturation levels and/or enhancing salivation (Chow et al., 1994, J. Dent. Res. 73: 26-32). In these in vivo studies, monocalcium phosphate monohydrate (MCPM; Ca(H.sub.2 PO.sub.4).sub.2 .multidot.H.sub.2 O) and an equimolar mixture of dicalcium =phosphate anhydrous (DCPA; CaHPO.sub.4) and tetracalcium phosphate (TTCP; Ca.sub.4 (PO.sub.4).sub.2 O) were used as chewing gum additives. These studies showed that both the MCPM and DCPA/TTCP gums increased the calcium and phosphate concentrations in saliva during a chewing period of 16 minutes. The extent of increase was much greater than those produced by gums containing DCPD. The degree of saturation with respect to tooth mineral was significantly increased by both experimental gums, with the greater increase being produced by the DCPA/TTCP gum.
U.S. Pat. Nos. 5,037,639, 5,268,167, 5,427,768, and 5,437,857, issued to Tung, disclose and claim the use of amorphous calcium phosphate (Ca.sub.3 (PO.sub.4).sub.2) and derivatives as chewing gum additives for tooth remineralization. However, evidence that ACP chewing gums actually remineralize teeth was not disclosed.
While some of the above additives have had some efficacy under some conditions, shortcomings have been associated with each. The DCPA/TTCP mixture requires an extensive preparation process: TTCP must be prepared in a furnace at a high temperature (1500.degree. C.) and then blended with commercially-available DCPA after each calcium phosphate salt has been ground to the desired particle size. ACP compounds must be precipitated in aqueous systems, thereby having variable composition and relatively undefined particles size. Also, the stability of ACP in gum base or a gel is likely to be limited, and a stabilizer may be required to achieve the desired shelf life.
Other calcium-containing compounds have been studied for their effectiveness in remineralization of teeth in situ. U.S. Pat. No. 5,378,131 to Greenberg disclosed the use of calcium glycerophosphate as a chewing gum additive for dental health benefits. This patent also disclosed the use of several other calcium compounds, including calcium lactate and calcium gluconate, to achieve an anticaries effect when used as a chewing gum additive. However, chewing gums containing calcium compounds as additives can only raise calcium concentration levels in saliva. In fact, phosphate concentration levels would be expected to be decreased as a result of chewing calcium-containing gums, based on the showing that saliva phosphate levels decrease with increased salivation stimulated by gum chewing (Chow et al., ibid.). Thus, these calcium-containing chewing gums disclosed by Greenberg are cariostatic, rather than anticarious. There is thus a need in the art for vehicles that release phosphate ions into the oral cavity in conjunction with increased calcium ion concentration to provide an anticaries effects not found in the gums known in the prior art.
In contrast to the recognized desirability of chewing gum as a vehicle for delivery of anticarious agents, candies have not been generally recognized as a means for delivering calcium and phosphate ions into the oral environment. A major reason for this is that sugar, the major ingredient of candies, is the chief culprit of dental caries. With the advent of sugar-free candies (i.e., candies that do not contain significant amount of fermentable carbohydrates), however, candies can be an effective means of delivering therapeutic agents for dental caries.